1. Field of the Invention
The present invention generally relates to a simplified logic circuit. More specifically, the present invention is directed to a DC to DC converter having a simplified logic circuit with a half-bridge rectifier, a synchronized rectification and a zero voltage switch (ZVS).
2. Description of the Related Art
Switching converters are widely utilized in changing electrical energy from one level of the voltage to another level of the voltage. As logic integrated circuits have migrated to lower working voltages in the search for higher operating frequencies. For instance, a power supply in a personal computer can provide for output voltage of 12 DC volts, however a CPU may need steady low voltages such as 5 DC volts, 3.3 DC volts or 2.5 DC volts. Lower voltages such as 1.82 DC volts are even required for a new generation of the CPU. As for the convert of DC voltages, it is not be completed by only a transformer and this convert should be achieved by rectifying, downgrading and re-rectifying. These converters are usually operated in a high frequency so as to cause the loss of electric energy, especially in voltages lower than 5 DC volts. Additionally, the above loss of electric energy is mainly because of the conductive loss and the switching loss in the electric circuit.
In conventional technology, there are so many methods to reduce the conductive loss and the switching loss in the electric circuit. For instance, a forward circuit, a half-bridge circuit, a bridge circuit, a self-oscillation circuit, a push-pull circuit, a synchronized circuit or a ZVS are usually used in the converters. When merely using one of the forward circuit, the half-bridge circuit, the bridge circuit, the self-oscillation circuit and the push-pull circuit to complete the switch convert, the efficiency of the electric circuit is low due to the high switching loss and thus the volume of the circuit becomes large. Therefore, in practice, the synchronized circuit or the ZVS may be added into the circuit to increase the efficiency of the same and to provide steady low DC volts, such as a combined circuit having the forward circuit and the synchronized circuit, a combined circuit having the push-pull circuit and the synchronized circuit, a combined circuit having the half-bridge circuit and the ZVS, a combined circuit having the bridge circuit and the ZVS, a combined circuit having the self-oscillation circuit and the ZVS, or a combined circuit having the push-pull circuit and the ZVS.
However, the volume of the above combined circuits with the synchronized function is too large and the control function is so complex that the components are not easily selected. Therefore, the manufacturing cost of the circuit increases accordingly. Although the volume of the combined circuits with the ZVS function can be effectively reduced, the problem that the control function is so complex that the components are not easily selected and thus the manufacturing cost of the circuit increases accordingly will be still existed. Additional, as the synchronized circuit in combination with the ZVS causes cross talk loss and makes this circuit more complex. Thus, it is not to combine these two circuits in DC to DC converter. For stated above, it is necessary to develop a low cost and high efficiency DC to DC converter.
Therefore, it is an object of the present invention to provide a DC to DC converter for combining a simplified synchronous rectification circuit and a zero voltage switch circuit, thereby the DC to DC converter can reduce the volume of the circuit and lower the manufacturing cost. Another object of the present invention is to provide a DC to DC converter having high switching efficiency on the primary side. Thus, the DC to DC converter can transport a voltage output without cross talk loss. Another object of the present invention is to provide a DC to DC converter transporting a voltage output with no ripples through by half-period turns switch. Thus, the total converting efficiency of the DC to DC converter is largely increased.
Another object of the present invention is to provide a DC to DC converter with a simplified circuit, thereby decrease the components of the DC to DC converter to lower the manufacturing cost.